1. Field of the Invention
The present invention relates generally to a reference signal generator for use with a time base corrector (TBC) for correcting a time base error of a color video signal reproduced from a VTR, and more particularly is directed to the reference signal generator oscillating in synchronism with the burst signal of the reproduced color video signal.
2. Description of the Prior Art
In general, a reproduced color video signal obtained from a video tape recorder has a time base error. As a method for correcting the time base error, it has been proposed that the reproduced color video signal is converted into a digital signal by using a TBC (time base error corrector), then memorized in a memory element the memorized digital signal being read out and reconverted into an analogue signal. In this case, the conversion of the video signal into a digital signal and the writing it into a memory are performed by a clock pulse with its repitition frequency corresponding to that of the reproduced horizontal synchronizing signal and its phase synchronized with the reproduced burst signal, and the read-out from the memory and the reconversion to an analogue signal are carried out by a clock pulse of a constant frequency.
In order to generate the clock pulse synchronized in phase with the reproduced burst signal, it is necessary to use a phase synchronizing circuit, namely the so-called APC (automatic phase control) circuit, which requires at least several cycles of a reference signal for the phase comparison. The burst signal has more than eight cycles but is with accurate phase only in one or two cycles of the mid portion and is not necessarily accurate in the cycles of its front and back sides. Therefore, when the burst signal of eight cycles or more is directly applied to the APC as a reference signal for the phase comparison, the clock pulse with its phase maintained accurate can not be derived therefrom.